Method for allocating resources for communication between transceiving terminals in communication system supporting device-to-device communication, and apparatus therefor

ABSTRACT

The present document relates to a method for a base station to efficiently indicate, to a transceiving terminal, a resource region to which control information and data are to be transmitted in a wireless communication system supporting direction communication between terminals, that is, D2D communication, and an apparatus therefor. To that end, the transmitting terminal receives, from a base station, resource allocation information associated with D2D communication, and on the basis of the resource allocation information received from the base station, transmits, to a receiving terminal, control information (SA) for D2D communication and data corresponding to the control information, wherein the resource allocation information comprises first resource region information for transmitting the control information, and the transmitting terminal acquires, on the basis of the first resource region information, a second resource region information for transmitting the data.

TECHNICAL FIELD

Following description relates to a method of allocating a resource fortransmitting control information (SA) and data between a transmission UEand a reception UE in a wireless communication system supporting directcommunication between terminals, i.e., D2D communication, and anapparatus therefor.

BACKGROUND ART

FIG. 1 is a diagram for explaining a concept of direct communicationbetween terminals to which the present invention is applicable.

A general communication scheme is served by an eNB for a plurality ofuser equipments (UEs). On the contrary, according to a D2D communicationscheme, as shown in FIG. 1, if a resource for D2D communication isallocated, direct communication can be performed between a UE 1 and a UE2.

When a UE performs communication with a different UE using a directradio channel, it may be able to use a discovery signal as a method ofdiscovering a counterpart UE of the communication. In this case,although the UE corresponds to a terminal of a user, if such a networkdevice as an eNB transmits and receives a signal according to acommunication scheme between UEs, the network device can also regardedas a sort of UEs.

In the following, a directly connected link between UEs is referred toas a D2D link and a link used for a UE to perform communication with aneNB is referred to as an eNB-UE link.

DISCLOSURE OF THE INVENTION Technical Task

Information on a radio resource, which is allocated for D2Dcommunication, is firstly received from a base station and used. Yet, atransmission UE (Tx UE) should transmit data and control information forthe data to a reception UE (Rx UE) within the resource allocated by thebase station.

If an Rx UE receives all blind decoding from a resource predetermined bya base station, such a problem as unnecessary battery consumption of aUE may occur.

The present invention intends to provide a method for a Tx UE toefficiently utilize a resource for transmitting control information anddata to an Rx UE and an apparatus therefor.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of transmitting a signal, which istransmitted by a transmission user equipment (Tx UE) to a reception userequipment (Rx UE) in a wireless communication system supportingdevice-to-device (D2D) communication, includes the steps of receivingresource allocation information related to the D2D communication from aneNB and transmitting control information (SA) for the D2D communicationand data corresponding to the control information to the Rx UE based onthe resource allocation information received from the eNB. In this case,the resource allocation information includes information on a firstresource region for transmitting the control information and the Tx UEcan obtain information on a second resource region for transmitting thedata based on the information on the first resource region.

In this case, the first resource region is arranged in an X RB unit, thesecond resource region is arranged in a Y RB unit, and the informationon the first resource region can include a first index indicating aspecific location among the first resource region arranged in the X RBunit.

And, the information on the second resource region may correspond toinformation indicating a specific location corresponding to a secondindex corresponding to a Y/X multiple of the first index among thesecond resource region arranged in the Y RB unit.

Preferably, the Y/X may correspond to integers, by which the presentinvention may be non-limited.

Meanwhile, the first resource region is repeatedly arranged in an X RBunit, an RB gap of a first size is formed between the first resourceregions repeatedly arranged in the X RB unit, the second resource regionis repeatedly arranged in an Y RB unit, and an RB gap of a second sizeis formed between the second resource regions repeatedly arranged in theY RB.

Preferably, the resource allocation information can indicate the controlinformation and information for transmitting the data using a singledownlink control signal format.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, atransmission user equipment (Tx UE, D2D UE) operating in a wirelesscommunication system supporting device-to-device (D2D) communicationincludes a transceiver configured to receive resource allocationinformation related to the D2D communication from an eNB, thetransceiver configured to transmit control information (SA) for the D2Dcommunication and data corresponding to the control information to areception user equipment (Rx UE) and a processor configured to controlthe transceiver to transmit the control information (SA) and the databased on the resource allocation information received via thetransceiver. In this case, the resource allocation information includesinformation on a first resource region for transmitting the controlinformation and the processor can obtain information on a secondresource region for transmitting the data based on the information onthe first resource region.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a method of operating an eNB in a wireless communicationsystem supporting device-to-device (D2D) communication, includes thestep of transmitting resource allocation information, which is used forallocating a resource configured to transmit control information (SA)for the D2D communication and data corresponding to the controlinformation to a reception user equipment (Rx UE), to a transmissionuser equipment (Tx UE) for the D2D communication. In this case, theresource allocation information includes information on a first resourceregion for transmitting the control information and the eNB can supportthe Tx UE to obtain information on a second resource region fortransmitting the data based on the information on the first resourceregion.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, an eNB operating in a wireless communication systemsupporting device-to-device (D2D) communication includes a transceiverconfigured to transmit resource allocation information, which is usedfor allocating a resource configured to transmit control information(SA) for the D2D communication and data corresponding to the controlinformation to a reception user equipment (Rx UE), to a transmissionuser equipment (Tx UE) for the D2D communication, and a processorconfigured to control an operation of the transceiver in a manner ofbeing connected with the transceiver. In this case, the resourceallocation information includes information on a first resource regionfor transmitting the control information and the processor can supportthe Tx UE to obtain information on a second resource region fortransmitting the data based on the information on the first resourceregion.

Advantageous Effects

According to the present invention, an Rx UE is able to efficientlyrecognize a resource in which control information and data aretransmitted by a Tx UE, thereby enhancing D2D communication performance.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining a concept of direct communicationbetween UEs to which the preset invention is applicable;

FIG. 2 is a flowchart for explaining an overall process of D2Dcommunication to which the present invention is to be applied;

FIG. 3 is a diagram for explaining a method of selecting a specificsubframe pattern via a dynamic control channel after a plurality ofsubframe patterns (SFs) are designated via a higher layer signal;

Unlike FIG. 3, FIG. 4 is a diagram for explaining a method of implicitlyindicating a subframe pattern;

FIGS. 5 and 6 are diagrams for explaining an operation of a UE thatchanges a subframe pattern;

FIG. 7 is a diagram for a method of allocating a resource by applying adifferent period or an offset to a different UE or a UE group;

FIG. 8 is a diagram for explaining a method of predetermining a locationat which data corresponding to control information is received;

FIG. 9 is a diagram for explaining a method of not decoding a partialsubframe only among subframes between control information and data;

FIG. 10 is a diagram for explaining a method of configuring a partialresource to be a common resource among two allocated resources when tworesource allocation methods are used in a manner of being mixed;

FIG. 11 is a diagram for various signals used for a D2D operation;

FIG. 12 is a diagram for a DCI format 0 in a LTE system;

FIG. 13 is a diagram for a DCI format for D2D according to oneembodiment of the present invention;

FIG. 14 is a diagram for an example of adding an Rx ID field accordingto one embodiment of the present invention;

FIG. 15 is a diagram for an example of adding an MCS field according toone embodiment of the present invention;

FIG. 16 is a diagram for a case capable of adjusting a length of an SAfield according to one embodiment of the present invention;

FIGS. 17 to 20 are diagrams for other embodiments of the presentinvention;

FIG. 21 is a diagram for explaining a case of configuring bits belongingto an RPT indication field by dividing the bits into two parts accordingto one embodiment of the present invention;

FIG. 22 is a diagram for explaining an example that D2D transmission ispermitted to a partial subframe only among the entire subframes;

FIG. 23 is a diagram for explaining a case of utilizing a plurality ofsets while a partial subframe is used for D2D transmission among theentire subframes according to one embodiment of the present invention;

FIG. 24 is a diagram for a location relationship between an SA RB and adata RB according to one embodiment of the present invention;

FIG. 25 is a diagram for a case of configuring a resource gap between anSA RB and a data RB according to one embodiment of the presentinvention;

FIG. 26 is a diagram for a case of not configuring a resource gapbetween data RBs while a resource gap is configured between SA RBsaccording to one embodiment of the present invention;

FIG. 27 is a diagram for explaining a device configured to perform theaforementioned operation.

BEST MODE Mode for Invention

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the present invention.

The following detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details. In some instances, knownstructures and devices are omitted or are shown in block diagram form,focusing on important features of the structures and devices, so as notto obscure the concept of the present invention.

As mentioned in the foregoing description, following description relatesto a method of allocating a resource for transmitting controlinformation (SA) and data between a transmission UE and a reception UEin a wireless communication system supporting D2D communication and anapparatus therefor. To this end, first of all, a system supporting D2Dto which the present invention is applied is explained in detail.

<Overall Processes of D2D Communication>

Overall eNB-to-D2D Tx (and/or Rx) UE scheduling for D2D transmission canbe classified as follows.

FIG. 2 is a flowchart for explaining an overall process of D2Dcommunication to which the present invention is to be applied.

As shown in FIG. 2, a D2D Tx UE can receive a scheduling grant from aneNB [S210] and this step is explained as an eNB scheduling grantprocedure in the following. In FIG. 2, although it is depicted as ascheduling grant is transmitted to the Tx UE from the eNB, the Rx UE canreceive the same information from the eNB as well.

In the step S210, two methods are proposed. A method #1 corresponds to amethod of allocating a resource via an RRC signal and the method ofcontrolling a detail dynamic operation such as an operation ofactivating/releasing a resource via a physical/MAC control channel(e.g., PDCCH). On the contrary, a method #2 corresponds to a method ofcontrolling a D2D operation such as resource allocation and/orscheduling information via a physical/MAC control channel.

In the aforementioned two methods, although it is able to determinescheduling information (e.g., MCS, RV, DM RS parameters, etc.) in amanner of receiving the information from the eNB, a UE can autonomouslydetermine the scheduling information as well. When the schedulinginformation is received from the eNB, if the method #1 is used, theinformation can be delivered via an RRC signal form or a control channelform such as PDCCH. If the information is delivered via the RRC signalform, since it is not necessary to include such a field as MCS, RV, DMRS parameter, etc. in a DCI format of PDCCH, it may be able to reduce alength of the DCI format by removing the field from the DCI format. Or,it may be able to perform transmission using a DCI format of anidentical length by applying a technology such as zero padding or thelike to the DCI format.

Since the method #2 does not have an RRC signal, it is difficult toapply the above-mentioned technology.

If a UE autonomously determines the scheduling information (MCS, RV,etc.), a corresponding contents field of PDCCH is not necessary in themethod #1 or the method #2. In this case, it may be able to remove thecontents field or it may be able to apply a zero padding method to afield not in use.

Method #1—RRC signal and dynamic control signal (e.g. (E)PDCCH, PHICH)based scheduling (e.g. semi-static scheduling) for SA (and data)

As a first detail procedure for the method #1, a D2D Tx UE can receivean RRC signal from an eNB and the RRC signaling can include resourceallocation information for overall resource configuration/SA (and data).

Similar to LTE SPS scheduling, the eNB can allocate a specific resource(or a specific resource set/group) via the RRC signal. The specificresource is allocated for D2D transmission.

The eNB is able to allocate a monitoring resource for D2D receptionusing a similar method. The eNB monitors a specific resource region(e.g., subframe(s), a set of resource blocks) and may be then able toperform blind demodulation on data. In this case, the monitoringresource may correspond to a resource to be monitored to perform blinddecoding on SA (Tx-to-Rx for D2D), a resource to be monitored to receivedata, or both of the resources.

As a second detail procedure, the eNB can transmit a dynamic controlsignal to the UE and the dynamic control signal may indicateactivation/deactivation of an allocated resource.

The second detail procedure corresponds to a method of indicatingactivation or deactivation of an allocated resource via RRC usingEPDCCH, PDCCH, PHICH, or a new channel. In case of using the PHICH, itmay be able to reserve a separate PHICH resource (index) to indicateactivation or deactivation of an allocated resource. Or, it may be ableto utilize a resource index used for allocating a D2D resource todetermine a PHICH resource (resource index linkage). In particular, aPHICH resource index is determined by combining uplink resourceallocation information (index) and an additional parameter with eachother by utilizing a characteristic of D2D using an uplink resource.When a D2D resource index (virtual index) is used, other parametersexcept the D2D resource index can be configured to be identical to LTE.

If a concrete resource is not designated by an RRC signal and a resourceis allocated in such a form as a resource group or a range, it may beable to deliver a precise resource location and a transmission parameterby utilizing a dynamic control signal of the present detail procedure.It may be able to use EPDCCH, PDCCH, PHICH or the like as a channel onwhich the resource location and the transmission parameter aredelivered. This operation can be used not only for SA scheduling butalso for indicating a data resource region, i.e., data scheduling.

An example of the operation is explained in the following.

As a concrete example of the operation, a method of indicating a timelocation of an SA resource and/or a data resource is explained. Ingeneral, a D2D subframe transmitted by a UE becomes a part of overall ULsubframes. The remaining UL subframes are used for performingcommunication with an eNB. Meanwhile, if a UE transmits a D2D signal ina specific UL subframe, it is difficult for the UE to receive a D2Dsignal of a different UE on an identical band of the specific subframe.This is because the signal transmitted by the UE acts as stronginterference.

A subframe pattern in which a D2D signal is transmitted and a subframepattern in which a D2D signal is received can be differently configuredin the aspect of a UE. As a method of reducing mutual interference byreducing frequency of using a time resource overlapped with each otherused by two adjacent UEs and solving the aforementioned problem, UEsdifferent from each other can differently configure a pattern of asubframe in which a D2D signal is transmitted. In particular, theproblem can be solved in a manner that an eNB appropriately designates asubframe pattern to be used for D2D transmission in consideration of adistance between the UEs (by identifying the extent of the mutualinterference).

Of course, if the subframe pattern is dynamically designated via EPDCCHor PDCCH, it is able to promptly correspond to a location change of aUE. Yet, there are many limitations in designating various subframepatterns using the restricted number of transmission bits of the EPDCCHor the PDCCH. As a method of reducing signaling burden, it is able tomake a UE autonomously select a subframe pattern instead of a subframepattern determined and indicated by an eNB. A UE can select a subframepattern using a pseudo-random scheme based on a UE ID of the UE (or, aUE-specific parameter including a similar characteristic). Or, the UEreceives minimum signaling information from an eNB and uses thesignaling information as a factor for determining a pseudo-random value.As a result, a subframe pattern can be pseudo-randomly selected. If anappropriate subframe set is provided and a pattern is randomly selectedfrom the subframe set, it may be able to solve the problem caused by theaforementioned interference.

To this end, an eNB delivers candidates of subframe patterns capable ofbeing potentially used to a specific UE via a higher layer signal suchas RRC and may be able to designate a subframe pattern to be practicallyused for transmission at specific timing via EPDCCH or PDCCH.

FIG. 3 is a diagram for explaining a method of selecting a specificsubframe pattern via a dynamic control channel after a plurality ofsubframe patterns (SFs) are designated via a higher layer signal.

In particular, as mentioned in the foregoing description, referring toFIG. 3, N numbers of subframes are assigned in advance via a higherlayer signal and an eNB designates a pattern to be used for D2Dtransmission by selecting one subframe from the N number of subframesusing PDCCH or EPDCCH. In the course of assigning the N number ofsubframe patterns in advance, the eNB can designate a form of a subframepattern practically applied to a subframe pattern #k. for example, theeNB can assign a subframe pattern in a bitmap form of a subframe whichis repeated with a prescribed period.

Unlike FIG. 3, FIG. 4 is a diagram for explaining a method of implicitlyindicating a subframe pattern.

Specifically, configuring a plurality of SF patterns via a higher latersignal is identical to that of FIG. 3. Yet, according to the presentexample, it may be able to provide a seed value for performingpseudo-random selection only among a plurality of the SF patternsinstead of indicating an SF pattern to be explicitly used viaPDCCH/EPDCCH. And, it may be able to configure an SF pattern to beselected using unique information of a D2D UE (e.g., an ID of the D2DUE, and the like) without utilizing the aforementioned control channel.

FIGS. 5 and 6 are diagrams for explaining an operation of a UE thatchanges a subframe pattern.

Specifically, FIG. 5 shows a case of using an explicit SF patternindication scheme and FIG. 6 shows a case of using an implicit SFpattern indication scheme. In this case, assume that a subframe patternis repeated with a period of 8 ms and {10001010} and {00111001} areassigned to a subframe pattern #0 and a subframe pattern #1,respectively, via a higher layer signal in advance.

An eNB designates a subframe pattern to be practically used by a UE viaPDCCH and the subframe pattern can provide information for selecting theexplicit SF pattern in FIG. 5 and information for selecting the implicitSF pattern in FIG. 6. The UE can perform a D2D operation according tothe information.

In order to perform the operation, it is necessary to designate asubframe pattern to be used using a partial field of PDCCH or EPDCCH. Asmentioned in the foregoing description, if DCI for a legacy UL grant isreused as DCI for D2D, an unnecessary field exists. The field can beutilized as a subframe pattern indicator. The field can include a DCIformat 0/1A indicator, a CQI request field, an NDI field, and the like.It may also be able to use a part of a DM RS cyclic shift field or anMCS/RV field using a plurality of bits.

If a resource for transmitting scheduling assignment and a resource fortransmitting a D2D data are designated to a UE at the same time via asingle PDCCH or EPDCCH, a subframe pattern for the scheduling assignmentand a subframe pattern for the D2D data can be respectively assigned toeach state designated by the field of the aforementioned DCI. Or, when apattern is pseudo-randomly selected, it may be able to deliver aparameter or a seed value determining a pseudo-random value. It may alsobe able to determine a subframe index by a pseudo-random value without apattern. In this case, it may also be able to deliver a parameter or aseed value determining the pseudo-random value. Although a subframepattern or a subframe index can be determined based on signalinginformation for determining the pseudo-random value only, the subframepattern or the subframe index can also be determined by combining thesignaling information and a unique value of a UE with each other.

Similar to semi-persistent scheduling, the aforementioned methodallocates a resource via RRC and can implement an operation ofdynamically using or cancelling a resource through a physical layer anda MAC layer control channel.

Method #2—(E)PDCCH Based Scheduling (Dynamic Scheduling)

This method corresponds to a method of indicating not only resourceallocation but also MCS, RV, NDI, power control, PMI and the like fordata demodulation to a D2D Tx UE (and/or a D2D Rx UE) using a controlinformation delivering channel (e.g., EPDCCH, PDCCH, PHICH, or newchannel) in a physical layer (or including a MAC layer) instead ofresource allocation via RRC.

The usage of an SG (scheduling grant) can be defined in various ways aswell as the aforementioned function. As a representative usage, the SGcan be used for the usage of indicating a fact that contents ofscheduling information has changed. In this case, the usage can bedivided into a case of maintaining a signaling format identical to theSG and a case of using a different signaling format. The schedulinginformation may indicate a change of a resource region designated by anRRC signal, a change of a resource to be used by a D2D Tx UE (and/or aD2D RX UE) in the designated resource region, a change of a resourceregion practically allocated by the SG, a change of a resource regiongroup, or a change of all or a part of SA contents.

The SA contents include various scheduling information including an RA.If one or more contents of the SA contents are changed, the change canbe indicated by the SG In this case, it may be able to use an SG of acompact form in a manner of reducing a bit field of the SG

It may be able to implement SG/SA update (e.g., resource re-allocation)via not only PDCCH and EPDCCH but also PHICH. A PHICH resource can beused for the purpose of indicating whether or not there is amodification in SG/SA. If there is a modification in the SG/SA, it isable to receive a modified content by monitoring the SG/SA. Inparticular, SG/SA modification notification is designated in advance andit is able to receive a modified SG/SA after time at which the SG/SAmodification notification is designated or during a designated timesection.

The modification notification has two meanings. One meaning is tomonitor and receive SG to identify a modified content by notifying afact that it is necessary to modify SA. Another meaning is to receive amodified SG (at a prescribed timing) because the SG has changed or theSG is expected to be changed. As mentioned in the foregoing description,the usage of the SG can be used not only for SA but also for datascheduling.

Referring back to FIG. 2, as mentioned in the foregoing description,having received the D2D scheduling grant from the eNB, the Tx UE cantransmit control information, i.e., SA, to perform D2D communicationwith the Rx UE [S220]. The step S220 is explained as a schedulingoperation between the Tx UE and the Rx UE in the following description.

In order to transmit the SA, the scheduling operation can be usedtogether with the methods mentioned earlier in the step S210.

Examples of information capable of being included in the SA aredescribed in the following (resource-related information for reception).

(1) Information related to resource for data reception

(2) RB allocation

(3) Number of patterns for retransmission

(4) Frequency hopping pattern

(5) SPS of data (including periodicity)

(6) Target ID

(7) MCS/RV of data

(8) Timing advance of data

Meanwhile, after the SG is received via the step S210, timing at whichthe SA is transmitted can be determined as follows.

It may be able to induce SA transmission by receiving the SG in asubframe n−k1 (k1 is an integer) under an assumption that a D2D Tx UE isaware of a subframe in which the SA transmission is available. Since aneNB identifies the subframe in which the SA transmission is availableand transmits the SG in accordance with the subframe, there may exist arestriction in transmitting the SG. When a receiver processingcapability of a UE is considered in LTE system, a value of the K1 maybecome around 4. According to the technological progress, it is able tosufficiently configure the K1 value by 2 or 3.

Having received the SG the UE is able to identify a location of asubframe in which data is transmitted at the same time. In particular,the usage of the SG may include not only SA scheduling but also datatransmission. Hence, the SG can include data transmission timing(subframe), frequency resource allocation, and the like.

Meanwhile, it may be able to perform a method of transmitting SA in aresource in which SA transmission is valid at the time that the SG isreceived and then prescribed time elapses. According to the method, aneNB does not identify the subframe in which the SA transmission is validin detail and transmits the SG based on timing at which a D2Dtransmission resource is requested.

If the SG is received, an available subframe capable of generating andtransmitting SA is identified based on the SG and the SA is transmittedto an available or valid D2D subframe (a valid subframe in terms of SAtransmission). Although the SG is received and a next subframe isavailable, it is unable to immediately transmit the SA. In order toreceive and process the SG generate relevant information as the SA, andprepare to transmit data, n+k2 is required (in this case, the k2 is aninteger). According to the technological progress, it is able toconfigure the K2 by 2 or 3. According to reception capability of a UE,the k2 may have various values including 1, 2, 3, 4, or the like.

If the k2 corresponds to 4, the SA is transmitted after 4 subframes fromthe timing of receiving the SG If an available subframe does not existimmediately after the 4 subframes, the SA is transmitted in a nextsubframe. If an available subframe does not exist again, the SA istransmitted in a next subframe. This rule can be comprehended as afastest subframe appearing after the n+4.

In this case, a subframe in which transmission is unavailable maycorrespond to all subframes not designated as a D2D transmissionsubframe. Or, such a subframe in which a synchronization signal istransmitted as 0 and 5 can be excluded from the available subframe. Or,such a subframe in which a paging signal is transmitted as 0, 4, 5, and9 can be excluded from the available subframe.

In this case, although a subframe is designated as a D2D subframe, if achannel (a channel similar to the WAN synchronization signal, BCHchannel) on which D2D essential information is carried is set to the D2Dsubframe, the subframe can be excluded from the available subframe inwhich the SA is transmitted. Or, it may be able to configure an SAtransmission-dedicated subframe and the SA can be transmitted in thesubframe only. After the SG is received, the SA is transmitted in theavailable subframe in which the SA is transmitted after a subframe n+k3.

Having received the SG the UE is able to identify a location of asubframe in which data is transmitted at the same time. In particular,the usage of the SG may include not only SA scheduling but also datatransmission. Hence, the SG can include data transmission timing(subframe), frequency resource allocation, and the like.

Referring back to FIG. 2, as mentioned in the foregoing description,having transmitted the SA, the Tx UE can transmit data to the Rx UE inresponse to the aforementioned SA [S230]. In general, D2D communicationcorresponds to the aforementioned communication.

Although it is not depicted in FIG. 2, an SG HARQ procedure for D2Dcommunication is explained in the following.

If the D2D UE receives the SG in the step S210, the D2D UE may send aresponse to the eNB in response to the SG In this case, as mentioned inthe foregoing description, the SG may correspond to control informationsuch as SPS activation/deactivation, resource allocation (schedulinginformation) control information, or the like.

If it fails to receive the SG, since it is unable to perform followingSA transmission or unable to apply a modified item for a previouslytransmitted SA content, SA prior to a modification is consistentlytransmitted. As a result, it may cause performance deterioration or asituation that communication is unavailable.

Hence, it may be necessary to have confirmation for SG transmission. Inorder to have the confirmation for the SG transmission, it may be ableto utilize a UL ACK/NACK mechanism. In particular, it may be able tosend acknowledgement using a legacy PUCCH structure or an embedded PUCCHto PUSCH form in response to the SG If the SG follows a PDCCH/EPDCCHformat or a mechanism, it is able to secure a PUCCH resource connectedto each DCI index. Hence, it is able to easily utilize the PUCCHresource for making a response to the SG

In this case, if contents included in the SG are received in a manner ofbeing divided into SA and data and if it is able to identify whether ornot an error occurs in a manner of dividing the contents into the SA andthe data, it is able to make a feedback on information at which an erroroccurs among SA scheduling information and data scheduling information.Since an error occurs on one of the information or both of theinformation, it is necessary to determine a response bit for both cases.1 or 2 bits can be sufficient enough for the response bit. Feedbackinformation can be delivered by utilizing a PUCCH channel.

When an SG2 is transmitted after an SG1 is transmitted, if a UE receivesthe SG2, the UE determines that the SG1 is not valid anymore. Timing atwhich the validity is determined is applied after a subframe n+k4 fromthe timing at which the SG2 is received. In this case, the k4 is aninteger and the k4 is determined in consideration of timing at which theSG2 is practically applicable. For example, 2, 3, and 4 may correspondto a typical value of the k4.

The SG1 and the SG2 can be transmitted at the same time. Or, the SG1 andthe SG2 can be transmitted in a manner of being aggregated into a singleDCI format. In case of performing a separate coding, a receiving end mayhave a separate success rate. It may be preferable for a UE to feedbacka result of the transmission to an eNB. To this end, the aforementionedPUCCH structure may be appropriated for the feedback.

D2D transmit power control can be implemented via the SG In particular,it may be able to deliver a TPC command by utilizing a TPC field or aDCI format 3/3A. In case of using the 3/3A, a specific field of the 3/3Acan be used as a D2D power control by reserving the specific field. Ausage of the specific field should be partitioned in advance via RRCsignaling.

The SG can be implemented in a manner of determining valid time. Inparticular, if prescribed time elapses after the SG is received, ifprescribed numbers of subframes are passed, or if prescribed numbers ofD2D subframes are passed, the SG is automatically invalidated.Similarly, it may use a timer. If prescribed time elapses, the timer isexpired and the SG is considered as invalid. Or, it may be able tosimply define that the SG is valid until a next SG is received. Or, twomethods can be applied at the same time. For example, when prescribedtime or prescribed number of subframes elapses, the SG is invalidated.In this case, if an SG is received before the prescribed time or theprescribed number of subframes elapses, a previous SG is invalidated.

<Transmission of D2D SA and Data>

When D2D communication is performed, D2D control information requiredfor demodulating D2D data can be transmitted via a channel (or a signal)separated from a D2D communication channel on which data is transmitted.And, when control information necessary for delivering a D2D discoverymessage is separately transmitted, it is also able to apply an operationproposed in the following.

The D2D control information can include all or a part of informationincluding an NDI (new data indicator), an RA (resource allocation orconfiguration), an MCS (modulation and coding scheme/set), an RV(redundancy version), and a Tx UE ID. It is able to differentlyconfigure a combination of control information components according to ascenario to which D2D communication is applied.

In general, since control information (CI) is utilized for demodulatinga data channel, the control information should be decoded prior to thedata channel. Hence, it is necessary to know locations of a time and afrequency resource to which the control information is transmitted andrelevant parameters required for performing the demodulation in advance.For example, in case of an LTE PDCCH, in order to make a specificlocation to which control information is transmitted to be known amongspecific symbols of every subframe, a transmitting end and a receivingend commonly use a UE ID-based hashing function. In case of an LTE BCH,an eNB and a UE share a fact that system information is delivered to aspecific symbol of a specific SF with a period of 40 ms with each other.

As mentioned in the foregoing description, it is necessary to deliversufficient demodulation-related information (parameter) to a UE inadvance to acquire control information.

In order to guarantee successful demodulation of D2D controlinformation, a transmission-related parameter (e.g., a subframe/slotindex, a symbol index, and an RB index) should be shared with a UE. Forexample, the D2D control information can be configured to be transmittedin all subframes designated as a D2D subframe (a subframe designated toperform D2D transmission), a subframe set including a specific index, ora subframe set of a specific period. A potential CI transmissionsubframe or a subframe set should be recognized by a UE in advance viasignaling or UE-specific information.

It is able to configure a resource region to which a D2D data channel isdelivered to be different from a resource region to which D2D controlinformation is delivered in time domain. In particular, the D2D controlinformation is periodically transmitted in a unit of designated time(or, while hopping with a designated time-frequency domain pattern),whereas the D2D data is delivered to a resource region indicated by thecontrol information only. Unlike a scheme of transmitting control anddata by binding the control and the data with each other, this indicatesthat an instance transmitting the control and an instance transmittingthe data are independently managed. When the control and the data aretransmitted in a manner of being separated from each other, it may beable to independently configure a parameter (scrambling, CRC, CRCmasking, demodulation sequence generation parameter, etc.) applied tothe control and the data. Or, it may be able to indicate a parameterapplied to the data through control information. In the latter case,since monitoring & decoding are attempted in a potential resource towhich the control information is transmitted using a potential parameter(e.g., explicit or blind decoding) and it is not necessary to performdecoding attempt in the rest of resource regions, it is useful forreducing power consumption.

Moreover, in case of demodulating data, since designated information isdemodulated only at designated timing by utilizing a parameter indicatedby the control information and resource region information, it may beable to reduce power consumption.

As an example for implementing the above-mentioned method, a pluralityof UEs perform blind searching on a specific resource region at specifictiming to obtain control information and control information matchedwith each UE is decoded. Whether or not the control information ismatched with each UE can be implemented based on UE-specific informationor UE-group specific (UE-group common). It may apply UE-group commonscrambling or CRC masking to make a UE perform (blind) decoding only ormake a plurality of UEs (a group or all UEs) perform decoding byapplying UE-specific scrambling or CRC masking to D2D controlinformation.

A UE or a UE group can obtain information related to data demodulationfrom control information which has succeeded in decoding. In this case,the control information includes not only explicit information includedin the control information but also a parameter (a predeterminedparameter and a parameter obtained from a given set via blind search)(e.g., scrambling, CRC masking, use resource information, referencesignal related parameters, etc.). Hence, it may be able to configureblind decoding not to be performed on data.

In order to obtain control information, a UE or a UE group performsblind decoding on control information using a specific parameter atspecific timing by utilizing unique information or information signaledin advance and obtains scheduling information related to datademodulation and various parameters used for generating and transmittinga control channel. The control channel related parameter and the decodedscheduling information (resource allocation information necessary fordemodulating data of a UE and explicit information such as NDI, MCS, TxUE ID) are used for decoding and demodulating a data channel.

Since a parameter obtained by performing blind search is used for acontrol channel as it is or a new parameter generated based on theparameter is used for generating a data channel, it is not necessary toperform parameter blind search on the data channel.

It may be able to differently configure a period of a control channeland a period of a data channel in time to make two information to betransmitted in an identical subframe (in terms of a UE or a UE-group).In particular, blind decoding is performed on a control channel in aspecific subframe and data of the identical subframe is demodulatedbased on the information. In this case, blind decoding is performed onthe control channel only while blind decoding is not performed on data.By doing so, it may be able to make blind decoding complexity depend onthe control channel only in the subframe.

In particular, blind decoding is performed on control information in thesubframe. When blind decoding is performed on data, if control and dataare transmitted together in an identical subframe, blind decoding trialis rapidly increasing. Hence, the number of UEs capable of beingdetected in a specific subframe through blind decoding can berestricted. In particular, if a transmission period of control, atransmission period of data and the like are fixed, the control and thedata can be transmitted together in an identical subframe in some casesaccording to a mutual period. If there exists a blind decoding trialrestriction in a subframe, it may face a situation of reducing a controland/or data channel blind decoding trial.

In order to reduce the aforementioned problem, it may be able to preventa decoding trial limitation caused by variation of decoding complexityin a manner of introducing blind decoding to a control channel only.Meanwhile, the degree of scheduling freedom for a data channel isincreasing. In particular, when a control channel and a data channel arelocated at an identical subframe, since there is no decoding complexitylimitation, although the control channel is periodically transmitted ina specific subframe, it is not necessary to avoid a subframe in whichthe control channel is transmitted when a subframe in which the datachannel is to be transmitted is determined.

If a control channel is detected once and transmission of data relatedto the control channel is transmitted in a specific subframe, it is notnecessary to transmit control information in a control channeltransmission opportunity subframe (control channel transmission period)during a time section until a subframe in which data is to betransmitted. Similarly, it is able to additionally configure controlchannel blind decoding (monitoring) not to be performed until a datasubframe in which a control channel is decoded and the data subframeindicated by control information in the aspect of a UE. By doing so, itmay be able to reduce power consumption. The above-mentionedconfiguration can be differently configured according to a UE.

Since it is able to differently configure a period of transmitting acontrol channel and a subframe offset according to a UE, it is able toknow a subframe in which monitoring is not performed according to a UE.In particular, if a UE decodes control information in a specificsubframe, the UE is able to know DRX performing duration inconsideration of a period of control information monitoring subframe ofthe UE and an offset. If the UE receives and modulates controlinformation (i.e., scheduling assignment), the UE is able to calculatethe duration of not performing control information monitoring (DRX) byappropriately utilizing a specific bit value, control informationsubframe period information, and the like carried on a subframe index, aUE ID, and the control information.

FIG. 7 is a diagram for a method of allocating a resource by applying adifferent period or an offset to a different UE or a UE group.

In FIG. 7, a resource used for transmitting control information isrepresented as C1 among resources allocated to a UE1 (or a UE-group 1)(it is able to know the resource by (E-)PDCCH, SIB, preconfigured,relaying by UE, etc.). A period of the C1 resource corresponds to aperiod #1.

Similarly, a resource used for transmitting control information of a UE2(or a UE-group 2) including a period #2 is represented as C2.

First of all, C1 information corresponds to a parameter related totransmission of Data #1. The parameter corresponds to variousinformations (e.g., scheduling information such as a DM RS sequence,MCS, RA, and the like) necessary for an Rx UE. C2 informationcorresponds to a parameter related to transmission of Data #2. Theparameter corresponds to various informations (e.g., schedulinginformation) necessary for demodulating the Rx UE. Secondly, the C1 andthe C2 represent parameters associated with the Data #1 and the Data #2and information related to scheduling information.

Since a UE is aware of a location of a subframe to be monitored by theUE in advance, the UE performs blind decoding on the subframe.

FIG. 8 is a diagram for explaining a method of predetermining a locationat which data corresponding to control information is received.

In FIG. 8, if it is known as C1 is decoded and data for the decoded C1is delivered in a data #1 subframe, monitoring is not performed under anassumption that the C1 does not exist in a subframe periodicallyreserved to transmit control information appearing after the C1. FIG. 8shows an example that control information monitoring and decoding arenot performed in the subframe reserved for transmitting the C1 existingbetween the C1 and the data #1. This can be regarded as a DTX operationperformed to reduce power consumption since it is able to know inadvance that it is not necessary to perform the control informationmonitoring and the decoding. More specifically, although a controlinformation subframe reserved for transmitting control informationexists between the control information and a data transmission subframeindicated by the control information, blind decoding skipping is notperformed on all subframes between the control information subframe andthe data transmission subframe. Instead, the blind decoding should beexcluded from monitoring subframes only when a predetermined conditionis precisely satisfied.

FIG. 9 is a diagram for explaining a method of not decoding a partialsubframe only among subframes between control information and data.

Referring to FIG. 9, blind decoding is performed on C11 and C13 whileblind decoding is skipped on C12. In particular, bind decoding is notskipped for all candidate control monitoring subframes between C11 anddata #11. For example, monitoring is performed to perform blind decodingon the last subframe among candidate subframes existing between the C11and the data #11. Or, if N number of scheduling information candidatesubframes exists between a scheduling information subframe and a datatransmission, it may be required to have such a rule that blind decodingskipping is not performed on the K number of candidate subframespositioned at the back only. It is able to configure a value of the Kaccording to system management.

If it is able to separately recognize a subframe used for transmissionand a subframe used for reception (if subframes of two typesdistinguished from each other exist since it is unable to performtransmission and reception at the same time due to half-duplexrestriction) among subframe information subframes, the blind decodingskipping principle can be applied to the subframe used for transmissiononly. If there is no distinction, it may apply the rule in considerationof both types.

If there exists the term of validity of scheduling information, a UE mayexpect that additional scheduling information does not arrive during theterm of validity. In particular, it is able to ignore schedulinginformation arrived during the term of validity.

Since a plurality of UEs use a scheduling information subframe together,a UE can calculate a subframe to be monitored by the UE using adifferent parameter such as an ID of the UE, a D2D subframe index, orthe like. This is similar to a case that a UE calculates a pagingsubframe to be monitored by the UE using a UE ID and a differentparameter, i.e., the UE calculates a subframe index to be received bythe UE after being woke up from a sleep mode.

FIG. 10 is a diagram for explaining a method of configuring a partialresource to be a common resource among two allocated resources when tworesource allocation methods (mode 1 and mode 2) are used in a manner ofbeing mixed.

The two resource allocation methods used in the present example areshown in Table 1 in the following.

TABLE 1 Signaling methods Resource (or Resource Pool) indication methods(to be used for the following transmission) Resource Being transmittedAllocation Scenarios For Scheduling Assignment For Data communicationMode 1 In-coverage SIB (or (E)PDCCH) SIB (or (E)PDCCH) (eNB (This can betriggered by (This can be triggered by schedules) D2D scheduling requestD2D scheduling request (D-SR)) (D-SR)) Edge-of- Via other forwardingUE(s) Via other forwarding coverage SIB or other sig. UE(s) forwardingSIB or other sig. forwarding Out-coverage Pre-configured or otherPre-configured or other Semi-static resource pool restricting theavailable resources for data and/or control may be needed D2Dcommunication capable UE shall support at least Mode 1 for in-coverageMode 2 In-coverage SIB (or (E)PDCCH) SIB (or (E)PDCCH) (UE selects)Edge-of- Via other forwarding UE(s) Via other forwarding UE(s) coverageSIB or other sig. SIB or other sig. forwarding forwarding Out-coveragePre-configured or other Pre-configured or other The resource pools fordata and control may be the same Semi-static and/or pre-configuredresource pool restricting the available resources for data and/orcontrol may be needed D2D communication capable UE shall support Mode 2for at least edge-of-coverage and/or out-of-coverage

According to the example of FIG. 10, C1 and P resource are configured tobe an identical time and/or frequency resource. FIG. 10 shows a casethat the time and/or frequency resource is configured as a commonresource (e.g., cell specific, UE-group-specific). According to themethod, when a resource allocation scheme is switched, it may be able touse a control channel as a fallback subframe to be monitored. Inparticular, the fallback subframe corresponds to a candidate subframe inwhich control information is transmitted. The candidate subframe shouldbe monitored when a mode is switched.

It is necessary for UEs to which a resource is allocated by the mode 1and UEs to which a resource is allocated by the mode 2 to perform blinddecoding on both a P resource region and a C1 resource region. In thiscase, UEs belonging to a cell may have a different mode. Moreover, a UEcan be configured by two modes.

In this case, the mode 1 and the mode 2 consider not only acommunication resource allocation scheme but also a case of beingapplied to D2D discovery resource allocation. Moreover, in the aspect ofa UE, it may be able to configure a discovery resource by the mode 1, itmay be able to configure communication by the mode 2, and vice versa. Ofcourse, it may be able to have a communication combination that the mode1, the mode 2, and discovery exist in a manner of being mixed in theaspect of a plurality of UEs. In this case, it may be able to introducea concept of a default resource set or a common resource set to the mode1 or the mode 2 to make a predetermined UE or UE group, an entire cell,or a D2D enabled UE monitor the common resource set.

Based on the aforementioned contents, a method of configuring a DCIformat of a D2D grant is explained in the following.

<Format of D2D Grant>

FIG. 11 is a diagram for various signals used for a D2D operation.

An eNB can inform D2D UEs of an SA resource pool and a data resourcepool via a higher layer signal. And, the eNB can inform the D2D UEs ofactivation of the resource via a D2D grant. The D2D grant can betransmitted via (E)PDCCH or the like.

Hence, as shown in FIG. 11, a Tx UE can transmit D2D SA and data to anRx UE using a given resource.

In FIG. 11, a D2D grant plays a role in allocating a resource requiredfor transmitting SA and data and delivering control information such asMCS and the like (i.e., scheduling information) in a D2D Tx UE. However,since it is necessary to schedule both SA transmission and datatransmission, the amount of control information is too much to configurea single DCI format. Yet, if two DCI formats are configured, signalingburden becomes huge. Hence, as a compromise plan, a method of schedulingboth the SA and the data with a single DCI format by appropriatelyconfiguring a field is proposed in the following.

FIG. 12 is a diagram for a DCI format 0 in a LTE system.

A DCI format 0 corresponds to a representative DCI format of uplinkscheduling and includes control information such as FH, RA, MCS, and thelike.

As mentioned in the foregoing description, it is able to carry SA anddata scheduling information only when two DCI formats shown in FIG. 12are used. A basic principle for integrating the two DCI formats into oneis to examine characteristics of D2D transmission, replace fieldscorrelated with each other in the course of controlling SA transmissionand data transmission with an integrated field, and configures a partnot including correlation as a separate field.

First of all, since the FH is commonly applied, one field is left only.The MCS field exists when an eNB notifies the MCS field. If a UEautonomously determines the MCS field, the field is not necessary toexist. The NDI and the RV can be similarly configured. In case of theTPC, it is preferable to differently apply the TPC to the SA and thedata. Hence, it may transmit two TPCs or it may be able to configure aTPC and an offset TPC according to the TPC. Due to the characteristic ofD2D, information such as an Rx ID and the like can be additionallyconfigured.

FIG. 13 is a diagram for a DCI format for D2D according to oneembodiment of the present invention.

Specifically, FIG. 13 shows a method of delivering an SA RA and a dataRA in a manner of separating the SA RA from the data RA. Bits shown inFIG. 13 are just an example. A size of bits can be differently definedaccording to necessity. In case of the SA RA, it may be able to notify astart point only. In case of the data RA, similar to a UL RA scheme, itmay be able to notify a start point of data and a length by delivering asingle RIV value. Although it is able to notify the start point and anend point using a separate field, an additional 1 bit is required forthe separate field. In particular, a data RA time hopping field is newlyadded. A value of the data RA time hopping field is used for indicatinga data subframe time pattern to be used for transmitting D2D data intime domain. In FIG. 13, a form delivering separate power controlinformation to the SA and the data is shown in the drawing. ZPcorresponds to zero padding. The ZP is filled with control informationaccording to necessity. The ZP may not be used or does not exist.

FIG. 14 is a diagram for an example of adding an Rx ID field accordingto one embodiment of the present invention.

A unique point of FIG. 14 is a DCI format field configuration which isconfigured in consideration of a point that an Rx ID is capable of beingdelivered (except an RA field distinction). This is because, similar tounicast, the Rx ID is usable for the usage of designating a target UE ora group ID. An order of fields of a DCI format shown in the drawing maychange.

FIG. 15 is a diagram for an example of adding an MCS field according toone embodiment of the present invention.

Specifically, referring to FIG. 15, MCS is added to RA field separation,time hopping, and an Rx ID. MCS information determined by an eNB isadded to a DCI format under an assumption that the eNB is more aware ofa D2D link compared to a D2D Tx UE (via a buffer status report, and thelike). Similar to a different drawing, ZP can be omitted. A TPC fieldcan be divided into two TPC fields or one field can be configured tohave information of the two TPC fields.

FIG. 16 is a diagram for a case capable of adjusting a length of an SAfield according to one embodiment of the present invention.

Specifically, referring to FIG. 16, a length of an SA field is adjustedto be smaller instead of including an Rx ID. This is feasible because anSA resource region is not directly designated in the SA field and anindicator indicating one of predetermined subframe pattern sets isincluded in a DCI format. In this case, a size of bits of the indicatoris reduced to 3 bits.

FIGS. 17 to 20 are diagrams for other embodiments of the presentinvention.

Specifically, FIG. 17 shows field configuration information when theRx_ID mentioned earlier in FIG. 16 is added and FIG. 18 shows a case ofadding DM RS CS information to a DCI format.

And, FIG. 19 shows a case that the Rx ID is removed and the DM RS CS ismaintained and FIG. 20 shows a case that the Rx ID is added to theembodiment of FIG. 19.

It may be able to make correlation exist between the RA fields of thetwo types. Assume that there exist an RA1 for SA and an RA2 for data. Inthis case, the RA1 may indicate a location of an SA resource region andinformation obtained from a combination of the RA1 and the RA2 mayindicate a location of a data resource region. In particular, it mayconsider there exist correlation between the SA resource region and thedata resource region. An RA field configuration configures an indicationbit in a manner of including correlation between RA field information byutilizing the correlation between the SA resource region and the dataresource region. On the contrary, information on the data resourceregion can be obtained based on information of the RA2 and informationon the SA resource region can be obtained based on a combination of theRA2 and the RA1. As a more concrete example, one RA2 indicates apractically transmitted resource region (time and frequency position)and another RA1 indicates a position apart from the time and thefrequency position of the RA2, i.e., offset position information only,and vice versa. In particular, the RA1 indicates precise resource regioninformation and the RA2 indicates offset information in response to theprecise resource region information. The resource region information andthe offset information are used for the SA resource region and the dataresource region, respectively.

<Single RA and Single RPT in D2D Grant>

An eNB transmits a D2D grant to a D2D TX UE to enable the D2D TX UE totransmit D2D to a D2D RX UE by utilizing a value indicated by Table 2 inthe following. Table 2 in the following is just an example. A fieldname, a length and a usage may vary.

TABLE 2 Field Name Length Use in D2D-Data-grant Flag forformat0/formal1A 1 RPT index differentiation Hopping flag 1 Use as isN_Ulhop   1 (1.4 MHz) Use as is 1 (3 MHz) 1 (5 MHz)  2 (10 MHz)  2 (15MHz)  2 (20 MHz) Resource block assignment   5 (1.4 MHz) Use as is forresource of data. 7 (3 MHz) Resource of SA is derived 7 (5 MHz) fromthis field. 11 (10 MHz) 12 (15 MHz) 13 (20 MHz) MCS and RV 5 Use as isfor data NDI (New Data Indicator) 1 RPT index CQI request (1 bit) 1 RPTindex TPC for PUSCH 2 Use as is Cyclic shift for DM RS 3 Use as is (or1~2 bit can be used for other purpose like RPT or target ID) UL index(TDD only) 2 Reserved Downlink Assignment 2 Reserved Index (DAI)

Or, it may be able to modify a structure shown in Table 2. For example,all DM RS related information can be deleted and all bits can be usedfor designating RPT. By doing so, it may be able to have a structureshown in Table 3 in the following. In this case, it may be able to use 6bits in total for the RPT.

TABLE 3 Field Name Length Use in D2D-Data-grant Hopping flag 1 Use as isN_Ulhop   1 (1.4 MHz) Use as is 1 (3 MHz) 1 (5 MHz)  2 (10 MHz)  2 (15MHz)  2 (20 MHz) Resource block   5 (1.4 MHz) Use as is for resource ofdata. assignment 7 (3 MHz) Resource of SA is derived 7 (5 MHz) from thisfield. 11 (10 MHz) 12 (15 MHz) 13 (20 MHz) MCS and RV 5 Use as is fordata TPC for PUSCH 2 Use as is RPT indication 6 New field UL index (TDDonly) 2 Reserved Downlink Assignment 2 Reserved Index (DAI)

In this case, bits belonging to an RPT indication held can be dividedinto two parts again (the two parts can be divided into top several bitsand the remaining bits in the RPT field. Or, the two parts can bedivided by a status represented by a single field).

FIG. 21 is a diagram for explaining a case of configuring bits belongingto an RPT indication field by dividing the bits into two parts accordingto one embodiment of the present invention.

A first part indicates how many subframes are granted for D2Dtransmission among the total subframes capable of performing D2D.

As an example, 2 bits can be used for the usage of indicating thesubframes in which D2D transmission is granted. An eNB can indicate alocation of a subframe capable of performing D2D to which one time SA isapplied via system information or a higher layer signal such as RRC.Hence, a UE is able to identify the number of subframes capable ofperforming D2D and becoming a target of the SA via the indication of theeNB. As a simple method, the number may become the number of subframesconfigured as a D2D data subframe between two adjacent SA periods. Inthis case, assume that total A number of subframes are configured as thesubframe capable of transmitting D2D data. If a UE receives a D2D grant,the UE is able to identify that the B number of subframes are grantedfor transmission of the UE via the bits among the A number of subframescapable of transmitting D2D data. Methods of identifying the number ofsubframes in which D2D transmission is practically granted using thefield is explained in detail in the following.

The number of practical D2D subframes, which is designated according toeach state of a corresponding part, can be determined in advance. Forexample, state ‘00’, ‘01’, ‘10’, and ‘11’ can be connected with 1, 2, 3,and 4 subframes, respectively.

The number of practical D2D subframes, which is designated according toeach state of a corresponding part, can be predetermined by a ratio tothe total number of subframes capable of performing D2D. For example,state ‘00’, ‘01’, ‘10’, and ‘11’ can be connected with floor (A/X)subframes, floor (2A/X) subframes, floor (3A/X) subframes, and floor(4A/X) subframes, respectively. In this case, the X corresponds to apredetermined number. It may be able to comprehend the number ofsubframes corresponding to 1/X, 2/X, 3/X, or 4/X as an operation ofallocating practical transmission via each state among the total Anumber of subframes capable of performing D2D.

The number of practical D2D subframes, which is designated according toeach state of a corresponding part, can be predetermined by such ahigher layer signal as RRC and system information.

Based on this, a UE is able to know that D2D transmission is granted inthe B number of subframes among the total A number of subframes.

FIG. 22 is a diagram for explaining an example that D2D transmission ispermitted to a partial subframe only among the total subframes.

In this case, it may be able to generate a plurality of candidatesubframe patterns based on a predetermined rule. Each of a plurality ofthe candidate subframe patterns determines a method of transmitting D2Din the B number of subframes among the A number of subframes. Then, aneNB can determine a pattern to be practically used among the candidatepatterns using a second part of the bits belonging to the RPT indicationfield.

As an example, 4 bits can be used as the second part. In this case, onepattern can be designated from among maximum 16 candidate patterns. TheeNB can dynamically control the number of subframes used fortransmitting D2D data by each UE in each SA period via theaforementioned methods. In particular, the number of subframes can becontrolled according to D2D data traffic amount of the UE.

Meanwhile, signaling on the B number of subframes in which transmissionof the UE is granted can be applied to D2D data transmission only. Incase of SA transmission, since it is not necessary to control the numberof transmission subframes according to a traffic situation, the numberof subframes used for transmitting SA can be fixed via a higher layersignal such as RRC or the like. Or, in order to perform control in aform identical to D2D data, a bit field for designating the number ofsubframes in which transmission of a UE is granted is reused and thenumber of subframes in which SA transmission is granted can also bedynamically controlled.

FIG. 23 is a diagram for explaining a case of utilizing a plurality ofsets while a partial subframe is used for D2D transmission among thetotal subframes according to one embodiment of the present invention.

In particular, although A (a subframe in which D2D data is transmitted)and B (a practically transmitted subframe) are determined, as shown inFIG. 23, there may exist a plurality of sets corresponding to the A andthe B. In particular, a plurality of sets such as 1, 2, 3, . . . , N mayexist. Assume that a set to be used is indicated by an eNB via a signal.In particular, the eNB indicates information on a set to be used inadvance via an RRC signal. An example of a different type of a set (setB) is described in the following.

Among the aforementioned control information fields, the RA field needsto have many bits to represent an SA position and a data position. Infact, the SA position and the data position are important for performingD2D transmission and reception. Yet, the number of bits required fortransmitting the D2D is not less, reducing the number of bitsconsiderably influences control channel performance. As a method ofintegrating RAs of two types into a single RA form, different RAinformation can be induced from single RA information.

For example, if RB x, x+1, . . . , x+a−1 are assigned to D2D data, an RBused as an SA (assume that the number of RBs of the SA corresponds to b)can be represented as follows.

First of all, if a data RA is allocated, a start point of an SA isidentical to a start point of the data RA and the SA occupies the bnumber of RBs. Of course, in this case, practical transmission of the SAcan be transmitted in a subframe identical to a subframe in which datais transmitted or a different subframe. Hence, an SA RB index can berepresented as x, x+1, . . . , x+b−1. Similarly, if the b number of RBsare occupied from the last point of the data RA, the SA is transmittedto b RB band in a manner of starting at (x+a−1)−b point. In particular,the SA RB index can be represented as x+a−b−1, x+a−b, . . . , x+a−1.

Meanwhile, it may be able to locate at the center of the data RA. Inthis case, the SA RB index can be represented as

${x + \left\lceil \frac{a - b}{2} \right\rceil},{x + \left\lceil \frac{a - b}{2} \right\rceil + 1},\ldots \mspace{11mu},{x + \left\lceil \frac{a - b}{2} \right\rceil + b - 1.}$

In this case, SA RB center may not correspond to data RB center. In somecases, the SA RB center may be apart from the center as many as 1 or 2RBs. If the number of the data BR has an even number and the number ofthe SA has an odd number, the SA is unable to locate at the center ofthe data RB. Hence, an index position greater than the center as many asone or an index position less than the center as many as one may becomethe SA center. If the number of the data RB has an odd number and thenumber of the SA has an odd number, two resource regions may have anidentical center. However, if the number of the data RB has an oddnumber and the number of the SA has an even number, the centers may havea difference as many as 1 RB. In summary, if the number of the data RBand the number of the SA RB identically have an even number of an oddnumber, centers of the two allocated resource regions are identical toeach other and the resource regions can be located at the center.However, if one of the number of the data RB and the number of the SA RBcorresponds to an even number and another one corresponds to an oddnumber, the resource regions are unable to be located at the center.Hence, a special rule is required for the above mentioned case. Inparticular, it is necessary to determine the center among an index(X_c−1) smaller than the center (center x_c) and an index (x_c+1)greater than the center. The center can be determined by a fixed valueaccording to a predetermined rule. Yet, since the center may varyaccording to a bandwidth size, an allocated resource size or ratio(data, SA), a transmission mode, an operation mode, or the like, thecenter can be configured by a higher layer signal. And, it is able toperform blind decoding on a location of the SA on the basis of thecenter and information obtained from the location information can beused for the usage of determining a transmission/operation mode.

Meanwhile, SA allocation is not available for all RB indexes. Forexample, there is a restriction that SA should be located at an indexcorresponding to a multiple of C. If a restriction is placed on a startpoint of the SA (if a start point of an RB index corresponds to amultiple of C), the start point can be defined as

$C{\left\lceil \frac{a - x + \left\lceil \frac{B - b}{2} \right\rceil}{c} \right\rceil.}$

In the aforementioned transmission scheme, if the SA and the data aredesignated by an identical subframe, the SA can be punctured or ratematched with the data.

In LTE RA, it may be able to indicate an RIV (resource indication value)introduced to a TYPE 2 contiguous RA. In this case, the RIV indicates astart RB (RB_start) and a length of RB (RB_length) via a predeterminedequation (conversion table). Hence, the parameter can be applied to theequation as it is.

And, since a location of the SA is included in a data transmission band,indication can also be performed by utilizing a subset of RIV. Forexample, as shown in Table 4 in the following, if RIV_data=16 issignaled in response to 5RB BW, a start position (RB_start) of the datacorresponds to 1 and a length (RB_length) corresponds to 4.

TABLE 4

Since the data transmission band corresponds to 4 RBs and the SA istransmitted in the band, as a method of indicating the SA, 4RB-basedRIV_SA table is configured as follows and it may be able to performRIV_SA signaling in accordance with the table. In particular, if a datatransmission band is determined, an RIV table is generated in accordancewith the bandwidth and an RIV for the SA is determined and transmitted.A reception procedure is performed inversely. A start point and a lengthof data are found out by receiving an SA RIV and a start point and alength of an SA are found out by receiving an SA RIV. Table 5 in thefollowing shows an example of the RIV table for the SA.

TABLE 5

In the example, a table for interpreting RIV=4 corresponding to SAresource region information is a value obtained from a table forinterpreting RIV=16 corresponding to data resource region information.

Additionally, since RIV_SA table is determined based on an RIV_SA value,although the RIV_SA value varies, it is able to know a length of thevalue. Hence, it is not difficult to perform decoding. If a partial bitis not used due to a variable length, a predetermined specific bit canbe used to enhance a coding gain.

Meanwhile, not only an RA but also an RPT (resource pattern oftransmission), which indicates a time-domain resource allocation patternof an SA subframe and a data subframe, can obtain an SA and a data RPTfrom a single RPT. It is preferable to configure an RPT (data, SA) fieldto indicate data and SA RPT at the same time like a DCI format shown inthe drawing.

Assume that an SA subframe pattern set exists and pluralities of RPTsexist in the set. Similarly, assume that a data subframe pattern setexists and pluralities of RPTs exist in the set.

SA RPT set={SA_pattern-1, SA_pattern-2, . . . , SA_pattern-N}

Data RPT set={Data_pattern-1, Data_pattern-2, . . . , Data_pattern-M}

For example, if a D2D grant DCI format RPT field receives such a valueas RPT=0010, the field recognizes the value as 2, selects SA_pattern-2for SA RPT, and selects Data_pattern-2 for data RPT. In this case, theSA_pattern-2 and the Data_pattern-2 do not mean an identical pattern. Inparticular, each pattern corresponds to a pattern selected from anindependent pattern set which is defined in accordance with its ownpurpose. In particular, although an identical value is indicated, an RPTpattern applied to the SA and an RPT pattern applied to the data aredifferent from each other.

In addition, when the number of the SA RPT patterns and the number ofthe data RPT patterns are compared with each other, it is highlyprobable that the number of the SA RPT patterns is less than the numberof the data RPT patterns. If the number of the SA RPT patterns is lessthan the number of the data RPT patterns, it may be able to use an SARPT value by performing modulo calculation on an RPT value of a DCIformat using a maximum number (N) of the SA RPT pattern. For example,when the number of the SA RPT patterns corresponds to 4 and the numberof the data RPT patterns corresponds to 8, if RPT index=6 is signaled asa D2D grant, an Rx UE uses a value resulted from performing modulocalculation on 6 by the total number of SA patterns (i.e., mod(6,4)=2)as an RPT pattern index. On the contrary, data uses 6 as a data RPTpattern index as it is. In particular, since a field of a DCI format anda signaling format are determined according to the number of data RPTpattern indexes, if the value exceeds the SA RPT pattern index, the SARPT pattern index can be determined using the modulo calculation.

<Mapping Relationship Between SA RB and Data RB>

In order to induce resource allocation information (location) of datafrom resource allocation information of SA or, in order to induceresource allocation information of SA from resource allocationinformation of data, there should be a consistent relationship betweenthe resource allocation informations. For example, assume that data #0RB index is induced from SA#0 RB index and data #k RB index is inducedfrom SA #k RB index. In this case, if an SA transmission unit is fixedby N_sa=2BRs and a data transmission unit is fixed by N_data=4RBs, itmay be able to represented as SA RB index *2=Data RB index.

FIG. 24 is a diagram for a location relationship between an SA RB and adata RB according to one embodiment of the present invention.

As a simple solution, it is able to fix a BW. Yet, in order toefficiently use a resource, it may be able to configure the number ofRBs to be changed. For example, it may be able to configure the numberof RBs to be semi-statically changed by informing a D2D UE of an SA RBsize and a data RB size via SIB or an RRC signal (or PD2DSCH). Theabove-mentioned method can include two methods. A first methodcorresponds to a method that an SA transmission unit (RB number, e.g.,2RBs or 4RBs) is fixed and a data transmission unit (RB number) variesfrom 1 RB to 100 RBs. A second method corresponds to a method that boththe SA transmission unit and the data transmission unit vary. First ofall, the first method is explained. If the SA is configured by 2 RBs andthe data is configured to vary with 2, 4, 6, 8 RBs, it is able to inducea data RB index from an SA RB index using a combination of an SAtransmission unit and a data transmission unit.

TABLE 6 If SA = 2, Data = 2 are signaled/configured => Data RB index =1*SA RB index If SA = 2, Data = 4 are signaled/configured => Data RBindex = 2*SA RB index If SA = 2, Data = 6 are signaled/configured =>Data RB index = 3*SA RB index If SA = 2, Data = 8 aresignaled/configured => Data RB index = 4*SA RB index If SA = 3, Data = 3are signaled/configured => Data RB index = 1*SA RB index If SA = 3, Data= 6 are signaled/configured => Data RB index = 2*SA RB index

If a data transmission unit is divided by an SA transmission unit and ashare corresponds to N_map, it is able to induce a data RB index bymultiplying an SA RB index by the N_map. For a simple implementation, itmay be able to restrict transmission unit/allocation units of the SA andthe data to have a relationship of integer multiple. If the SA unitcorresponds to 2 RBs, the data unit uses a transmission unit of amultiple of 2 (e.g., 2,4, 6, or 8) or a transmission unit of the powerof 2 (2̂x) (e.g., 2, 4, 8, 16 . . . ) only (signaling or configure orequation or calculation). For example, it is able to configure the N_mapto be an integer all the time. This rule can also be used for the usageof checking an error in a signaling or configuring procedure.

If an SA is detected, an SA RB index is found out, and the SA RB indexis multiplied by an N_map value, a data RB index is induced. In thiscase, for clarity, a start RB index is explained as an example. Yet,various values including a center RB index, an end RB index, and thelike can be used as a reference RB index as well.

If a resource gap (e.g., reserved RB, guard RB,) is introduced in thecourse of allocating an SA or a data due to additionally considereditems such as in-band emission and the like, it is necessary to inducean SA RB index or a data RB index in consideration of an RB used for theresource gap.

FIG. 25 is a diagram for a case of configuring a resource gap between anSA RB and a data RB according to one embodiment of the presentinvention.

In case of using a resource gap, it is necessary to signal the resourcegap via a high layer signal. For example, as shown in FIG. 25, in caseof using a reserved gap of 1 RB, it is necessary to calculate a data RBindex under an assumption that the reserve gap is configured between thedata transmission units and/or the SA transmission units.

If SA=2, Data=4 are signaled/configured=>Data RB index (i)=2*SA RB index(i)+i*reserved RB gap (e.g. 1 RB), i=1, 2, 3, . . . .

It may be able to configure various rules to induce a data RB index froman SA RB index according to an SA RB allocation method (including areserved gap).

FIG. 26 is a diagram for a case of not configuring a resource gapbetween data RBs while a resource gap is configured between SA RBsaccording to one embodiment of the present invention.

Referring to an example of FIG. 26, SA RBs are repeated in a unit of 2RBs for a simple configuration and a location of an RB can be directlyobtained via an SA RB index using a gap of 2 RBs, by which the presentinvention may be non-limited.

As a different method, it may consider a case that SA and data ofdifferent transmission units coexist in an identical subframe. It may beable to configure a data RB index to be induced from an SA RB index in amanner of configuring a plurality of transmission units and dividing anallocation region. It may be able to configure a location of SAallocated in a transmission unit of 2 RBs to be different from alocation of SA allocated in a transmission unit of 3 RBs, configure aboundary between the locations, and reflect the boundary to calculation.

FIG. 27 is a diagram for explaining a device configured to perform theaforementioned operation.

A wireless device 800 corresponds to a specific UE 1 (Tx UE) of theaforementioned description and a wireless device 850 may correspond to adifferent specific UE 2 (Rx UE) of the aforementioned description. And,if the UE 1 performs communication with an eNB, the wireless device 850may correspond to the eNB.

A UE 1 can include a processor 810, a memory 820, and a transceiver 830.A UE 2 850 can include a processor 860, a memory 870, and a transceiver880. The transceiver 830/880 is configured to transmit/receive a radiosignal and can be executed in a physical layer. The processor 810/860 isexecuted in a physical layer and/or an MAC layer and is connected withthe transceiver 830/880. The processor 810/860 can perform theaforementioned interference control procedure.

The processors 810 and 860 and/or the transceivers 830 and 880 mayinclude an Application-Specific Integrated Circuit (ASIC), a chipset, alogical circuit, and/or a data processor. The memories 820 and 870 mayinclude a Read-Only Memory (ROM), a Random Access Memory (RAM), a flashmemory, a memory card, a storage medium, and/or a storage unit. If anembodiment is performed by software, the above-described method may beexecuted in the form of a module (e.g., a process or a function)performing the above-described function. The module may be stored in thememories 820 and 870 and executed by the processors 810 and 860. Thememories 820 and 870 may be located at the interior or exterior of theprocessors 810 and 860 and may be connected to the processors 810 and860 via known means.

The detailed description of the preferred embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the preferred embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

INDUSTRIAL APPLICABILITY

The present invention can be applied to various wireless systemssupporting direct communication between wireless devices.

What is claimed is:
 1. A method of transmitting a signal, which istransmitted by a transmission user equipment (Tx UE) to a reception userequipment (Rx UE) in a wireless communication system supportingdevice-to-device (D2D) communication, comprising the steps of: receivingresource allocation information related to the D2D communication from aneNB; and transmitting control information (SA) for the D2D communicationand data corresponding to the control information to the Rx UE based onthe resource allocation information received from the eNB, wherein theresource allocation information comprises information on a firstresource region for transmitting the control information and wherein theTx UE obtains information on a second resource region for transmittingthe data based on the information on the first resource region.
 2. Themethod of claim 1, wherein the first resource region is arranged in an XRB unit, wherein the second resource region is arranged in a Y RB unit,and wherein the information on the first resource region comprises afirst index indicating a specific location among the first resourceregion arranged in the X RB unit (where X and Y correspond to integers).3. The method of claim 2, wherein the information on the second resourceregion indicates a specific location corresponding to a second indexcorresponding to a Y/X multiple of the first index among the secondresource region arranged in the Y RB unit.
 4. The method of claim 3,wherein the Y/X corresponds to integers.
 5. The method of claim 1,wherein the first resource region is repeatedly arranged in an X RBunit, wherein an RB gap of a first size is formed between the firstresource regions repeatedly arranged in the X RB unit, wherein thesecond resource region is repeatedly arranged in an Y RB unit, andwherein an RB gap of a second size is formed between the second resourceregions repeatedly arranged in the Y RB unit (where X and Y correspondto integers).
 6. The method of claim 1, wherein the resource allocationinformation indicates the control information and information fortransmitting the data using a single downlink control signal format. 7.A transmission user equipment (Tx UE, D2D UE) operating in a wirelesscommunication system supporting device-to-device (D2D) communication,comprising: a transceiver configured to receive resource allocationinformation related to the D2D communication from an eNB, thetransceiver configured to transmit control information (SA) for the D2Dcommunication and data corresponding to the control information to areception user equipment (Rx UE); and a processor configured to controlthe transceiver to transmit the control information (SA) and the databased on the resource allocation information received via thetransceiver, wherein the resource allocation information comprisesinformation on a first resource region for transmitting the controlinformation and wherein the processor is configured to obtaininformation on a second resource region for transmitting the data basedon the information on the first resource region.
 8. The D2D UE of claim7, wherein the first resource region is arranged in an X RB unit,wherein the second resource region is arranged in a Y RB unit, andwherein the information on the first resource region comprises a firstindex indicating a specific location among the first resource regionarranged in the X RB unit (where X and Y correspond to integers).
 9. TheD2D UE of claim 8, wherein the information on the second resource regionindicates a specific location corresponding to a second indexcorresponding to a Y/X multiple of the first index among the secondresource region arranged in the Y RB unit.
 10. The D2D UE of claim 9,wherein the Y/X corresponds to integers.
 11. The D2D UE of claim 7,wherein the first resource region is repeatedly arranged in an X RBunit, wherein an RB gap of a first size is formed between the firstresource regions repeatedly arranged in the X RB unit, wherein thesecond resource region is repeatedly arranged in an Y RB unit, andwherein an RB gap of a second size is formed between the second resourceregions repeatedly arranged in the Y RB unit (where X and Y correspondto integers).
 12. The D2D UE of claim 7, wherein the resource allocationinformation indicates the control information and information fortransmitting the data using a single downlink control signal format. 13.A method of operating an eNB in a wireless communication systemsupporting device-to-device (D2D) communication, comprising the step oftransmitting resource allocation information, which is used forallocating a resource configured to transmit control information (SA)for the D2D communication and data corresponding to the controlinformation to a reception user equipment (Rx UE), to a transmissionuser equipment (Tx UE) for the D2D communication, wherein the resourceallocation information comprises information on a first resource regionfor transmitting the control information and wherein the eNB supportsthe Tx UE to obtain information on a second resource region fortransmitting the data based on the information on the first resourceregion.
 14. An eNB operating in a wireless communication systemsupporting device-to-device (D2D) communication, comprising: atransceiver configured to transmit resource allocation information,which is used for allocating a resource configured to transmit controlinformation (SA) for the D2D communication and data corresponding to thecontrol information to a reception user equipment (Rx UE), to atransmission user equipment (Tx UE) for the D2D communication; and aprocessor configured to control an operation of the transceiver in amanner of being connected with the transceiver, wherein the resourceallocation information comprises information on a first resource regionfor transmitting the control information and wherein the processor isconfigured to support the Tx UE to obtain information on a secondresource region for transmitting the data based on the information onthe first resource region.